1. Technical Field
The present invention relates to an eyeglass lens measuring apparatus for measuring optical properties of an eyeglass lens, a method for distinguishing an upper portion from a lower portion of an eyeglass lens, and a point marking adapter.
2. Related Art
A known eyeglass lens measuring apparatus (such as a lens meter) obtains optical properties of a lens by, for example, projecting measurement light flux onto the lens and then receiving the measurement light flux that have passed through the lens with a light receiving device (see JP-A-2006-292650, for example). When the optical properties of the eyeglass lens are measured by such an eyeglass lens measuring apparatus, it is known to implement a so-called point marking operation. In the point marking operation, the lens is provided with mark points for clarifying a measurement location.
The mark points provided by the point marking operation normally include one point on a measurement optical axis, and two points on a line passing the one point, for three points in total. Of those three points, the one at the center mainly indicates the optical center of the lens, while the other two points indicate a reference for an astigmatic axial angle (see FIG. 11).